Pneumatic separator for pulverizing-mills.



E. J. STECKLE, PNEUMATIC SEPARATOR FOR PULVERIZING MILLS. APPLICATION FILED 1m31. I9Is.

1,246,344. mmm Nov. 13,1917.

2 sHEETs-SHEET I.

IIIIIIIII' Emdc" INVENToR,

W1 TNESSES:

E.1.sTEcKLE PNEUMATIC SEPARATOR FOR PULVERIZING MILLS.

I APPLICATION FILED IAN.3I| I9I6.

1,246,344. Patented Nov; 13, 1917.

2 SHEETS-SHEET 2. Y

Affawzey nnwm .1. srEcnLn, or mxoN, rumors.

PNEUHTIC SEPABATB FOB P'UI'vViERIZING-MILLS.

Specification of Letters Patent.

Patented Nov. 13, 1917.

Application ledanuery 81, 1916. Serial No. 75,418.

To all whom t ma concern."

Be it known tha I, EDWARD J. STECKLE, a citizen of the United States, residing at Dixon, inl the countyiof Lee and State of Illinois, have invented a new and useful Pneumatic Se arator for Pulverizing-Mills,

of which the ollowing is a specification.

The present invention relates to an attachment for pulverizing mills for separating the ne material from the coarser particles, and has for an object to provide a device which effects this separation by pneumatic means, and which utilizes the pneumatic means for positively returning the lar er or coarser particles to the pulverizing mill to be reground.

Another object of this invention is to provide an apparatus which is of such form and construction that the material delivered from 'the crushing' or pulverizing mill is divided into'a number of different streams, and is delivered in horizontal lms or sheets,

which are given a rotary spiral motion, and

a draft of air is passed upwardly through the ilm to lift therefrom the lighter particles, and allow the heavier or coarser particles to drop down into the bottom ,of a chamber. In carrying out `this object of the invention, provision is also' made for preventing the return of the particlesto the throat or passage leading from the pulverizing mill, so that at no Vstage of operation is it possible to choke the mill or any part of the apparatus.

A further object of the present invention -is toA provide a pneumatic circuit leading from the delivery side or part ofthe mill, which is preferably of the rotary hammer type, as will be hereinafter described and. as is shown in the accompanying drawings, and -to return this air current to the mill at substantially the central portion thereof, so that the suction action of the mill serves as an auxiliary inducer to force the continuous draft throughV the circuit.

A still further object of the invention is to provide a catch chamber vto receive the coarser particles which are too heavy for the suction or air current 'to lift, and to connect the bottom of the chamber with discharge pipes connecting with the return pipe of the air circuit, so that the suction in the return pipe effects a positive feeding of the coarser particles from; 'the chamber back into the central portion of the pulverizer, so that thematerial may be reground.

There are various other equally important objects and advantages of this invention, which will be more clearly brought'out in the following description of the present preferred embodiment of this -invention, the same being illustrated in the accompanying drawings, wherein- Figure 1 is a front elevation of a pulverlzing machine of the rotary hammer type,

having the improved .pneumatic separator attachment applied thereto.

Fig. 2 is a side elevation of the same, parts of the device being shown in section.

Fig. 3 is a horizontal sectional view, enlarged, taken on the line 3-3 of Fig. 2, and showing the interiorof the separating chamber and the delivery nozzles in the lower part thereof.

Referring to these drawings, 10 designates the casing or body portion of a pulverizing or grinding mill, shown in the present instance as eing` of the hammer type, and having the rotary head 11, provided with radiating hammer arms 12, coperating with grindmg plates 13, to pulverize or crush the material, which is fed into the mill, through the hopper 14. The head 11 is mounted on a transversely extending shaft 15 on one end of which is arranged a balance or fly wheel 16, while the opposite end is provided with a belt receiving pulley 17, by means of which the pulverizing mill is adapted to be turned. As shown to advantage in Fig. 2, the mill is provided at its top,.and at one side of the central shaft 15, with an upwardly extending throat or outlet passage 18, through which the material crushed is delivered by.

centrifugal force, and by the air current produced by the rapid rotation of the head 11 and the hammers 12. The material is thus thrown upwardly through the throat 18 by centrifu al force. The throat 18 is provided with a plurality of bales 19, which are in the form of longitudinally spaced Aapart slats, extending transversely in the throat 18, and being pivoted at their opposite ends in the sides of the throat. The

slats or baffles 19 are adapted to be turned into horizontal position, and to overlap more -108 or less to open and close the throat to the desired extent, and to thus control the size of the crushed material which passes out of the casing of the mill 10. If the material is too large to pass between 'the baiies 19, it is deiected backwardly into the casing and taken up` by the hammers 12, so that the material is carried back into the machine and is further ground. However, the baiies 19 are not sufficient to correctly and accurately gage the size of the particles and deliver the same at a constant or uniform size.

The top of the throat 18 is provided with an uptake chamber 20, the bottom of which preferably tapers, as shown to advantage in Figs. 1 and 2, and is providedl with a air of horizontal diametrically extending mverted V-shaped receivers 21, which intersect centrally of the casing to divide the bottom of the same into four compartments, which flare upwardly, so as to provide oppositely inclined sides to receive material dropped into the bottom of the uptake chamber 20, and direct the same to the relatively small bottoms in the several compartments. The material passing the baiiies is forced upwardly into the receivers 21, and is delivered therefrom through a plurality of nozzles 22, which project from one side of each receiver 21, and extend circularly and in the same direction, and which also project upwardly at a slight angle, as shown in Figs. 2 and 3. f Y

Fitting into the top of the uptake chamber 20 is a suction pipe 23, which leads into the intake of a fan 24, the same being mounted upon a suitable frame 25, placed in the upper end of a collecting hopper 26, and delivering thereto at one side of the hopper to produce a cyclone separator, wherein the articles taken upby the current of air rom the uptake chamber are permittedto fall into the bottom of the relatively large hopper 26, while the air which is delivered in a spiral current to the top of the hopper is drawn off through the return pipe 27. It will be noted from Fig. 2 particularly, that the end of the return pipe emerging from the top of the hopper 26 is relatively large, as at 28, while the diameter, or cross sectional area, of the pipe 27 decreases gradually from the end 28 to the mill 10, to which the current ofair is returned. In order to equalize the pressure of the air at the opposite sides of the mill, the return pipe 27 is branched, as at 29 to provide two arms or portions, which extend downwardly at the opposite sides of the device, and which deliver into the opposite sides of the casing 10, as at 30, slightly above the shaft l5.

As before mentioned, the bottom of the uptake chamber 20 is divided into four parts or pockets, into which the heavier or coarser material is received. From the relatively ,small bottoms of these pockets or compartments, discharge pipes 31 lead, the same extending downwardly and opening at their lower ends into the sides of the adjacent return branches 29 of the air circuit. The suction in the branches 29, which is caused not only by the current of air forced into the hopper 26, but also by the action of the hammers 12, creates a suction in the pipes 31, and draws outwardly therethrough the heavier particles from the compartments or pockets in the chamber 20. rl`he particles are thus drawn into the lower ends of the branches 29, and are forced into the casing 10, and are consequently reground. At a point in the pneumatic system, preferably in the top of the return or pressure pipe 27, a vent 32 is provided, the same having therein a valve 33 to control the outlet of air forced through the pipe 27 from the hopper 26. As the fan 24 creates a suction upwardly through the pipe 23, through the uptake chamber 20, and through the mill 10, the induced current of air thus produced may be'regulated more or less by manipulating the valve 33 to control the passage of air therethrough to thus vary the lifting power of the induced current and adjust the device to a nicety in the separation of the iner particles from the coarser ones. y

The bottom of the collecting hopper 26 may beprovided with a trough 34, in which av conveyer 35 is mounted so as to continuously feed the relatively fine selected material from the bottom of the hopper to 'any suitable point of discharge.

In the operation of the improved device, material is fed through hopper 14 into the casing 10, and is, in the usual manner, ground or pulverized to a certain extent and drawn upwardly into the throat 18. The material is impinged against the baffles 19, and it will be noted that the baiies are arranged at such an angle that they provide a plurality of more or less restricted passages in the throat 18, so that material of a predetermined size only is permitted to pass through the throat. The larger particles of the material are defiected back into the casing 10 and reground. The material, which passes upwardly through the throat 18is carried therethrough, not only by the air pressure from the revolving hammers 12, but also by reason of the induced draft produced'by the action of the fan 24'. The material is carried up into the radiating andl intersecting receivers 21, where it is drawn into the respective nozzles 22, and carried upwardly therethrough in a circular path and delivered substantially tangentially within the chamber 20, so that the material is divided up into a plurality of streams, which are whirled in cyclonic fashion around the interior of the uptake casing 20. This acp tion pipe 23. The heavier particles are more atliberty to falle into thebottom of thechamber 20`by` reason ,of this spreading out .and dividing of the material. The disposiof the receivers and bedefiected by the oppositely inclined walls thereof into the bottoms of the various compartments. As the nozzles 22 are relatively small in diameter as compared with the cross sectional area of thereceivers and of the chamber 20, the material is given increased impetus or velocity in passing through the nozzles, so that the suction through the nozzles is comparatively great and no chance is made possible of the blocking or clogging up of the nozzles. Furthermore, the restricted areas 'of the nozzles effect the expulsion of the material therefrom with comparatively great force, so that the material spreads outwardly from the ends of the nozzles and spreads into a relatively broad spiral stream. The induced current holds the liner particles in suspension and draws the same upwardly from the chamber 20, but allows the gradual fall of the heavier particles from the whirling'l stream to thus effect the gradual and posi-l tive separation of the different grades of the material. y

From the uptake chamber 20, the material is carried through the section 23 and fan 24, into the hopper 26. It is delivered in the hopper at one side thereof and substantially tangentially thereto, so that a whirling o'r spiral stream of air and material is produced. As the hopper 26 is relatively lge, the force of the air suction or pressure is lost, and the material is permitted to drop into the bottom of the hopper, while the air is caused to pass upwardly through the relativelyrrlarge end 28 of the return or pressure pipe 27. The air passes through the pipe 27, and through the branches 29 into the opposite sides of the casing 1 0, so as to return the' air substantially to the central portion of the rotary part of the mill, to thus take advantage of `the suction created at the central portion of the mill, as the hammers l2 are revolved. This inward flow of air through the pipes 29 into the casing 10 creates a suction in the pipes 31, which communicate .with the lower end of the chamber 20, so that the heavier particles of material which fall into the bottom of the chamber and are deflected into the pipes 31,

are positively drawn by the air current down into the inner ends or bottoms `of the branches 29 and forced into the casing 10 of theA mill, and into the path of the rotary hammers l2. It is thus observed that not` the mill to be recrushed, and the positive means of returning this material to be recrushed is also. utilized in separating the particles.

It will thus be readily understood .that a very eliicient, economical, and practical de-A vice is provided for separating vthe materialand adJusting the device to produce a finished article of the desiredl ineness, and

also that the material `which is rejected by the separator is positively returned to the mill, without the provision of exterior or. `secondary means. l

This whirling or circular motion of the material which issues from the nozzles 22 is produced by the impact of the material.

against the inner cylindricall -wall of the uptake chamber 20, which chamber is, as shown 1n Flg. 3, cylindrical in cross section, whereby the materialwhich is delivered from the nozzles at substantially a tangent to the chamber is directed in a curved path and at the same time is drawn upwardly by the suction of the induced current, so that a whirling spiral action is imparted to, the material in the chamber 20. The chamber 2() may be provided with any number of pockets or compartments in the bottom, and any number of nozzles, which are suiiicient to receive, and to eject the ma terial and lpermit the choking of the device.

t 1s, of course, understood that it is within the spirit of the invention to modify and change the above specifically set forth structure, as far asv is permissible .within the scope of the following claims.

What is claimed is l. The combination with a rotary pulver izing mill, provided at the top with an upwardly extending throat through which the `material is delivered by centrifugal force, of an uptake chamber Ihaving a closed bottom, said bottom serving as a top for the throat, a nozzle communicating with the throat through the bottom and extending upwardly above the bottom to deli/ver the ground material tangentially within the chamber, means for drawing oft the light particles of ground material from the top of the chamber, and means for returning the coarse particles of material from the bottom of the chamber to the mill.

2. rlh'e combination with a rotary pulverizing mill, of an uptake chamber having a closed bottom formed with a plurality of compartments, means for delivering the ground material from the mill against the underside of said bottom, a plurality o f nozzles corresponding in number to the compartments and opening through said bottom and extending upwardly therefrom to deliver the ground material from'beneath the bottom into the chamber over said compart- 'ments, means for drawing o the light parof said chamber, and means for returning the heavy particles from said compartments in the bottom of the chamber to the mill.

3. The combination with a pulverizing mill, of a separating chamber having a throat communicating with said mill and with an outlet pipe at its upper end, nozzles communicating with said throat and extending upwardly and circumferentially into said separating chamber, means for creating a draftv through said pulverizing mill and separating chamber, and means at the bottom of said separating 'chamber to allow the heavier particles of the material to pass through.

4. The combination with a pulverizing mill, of a separating chamber having a plurality ofcompartments in its lower end which have closed bottoms, and means for feeding a separate stream of 'ground material from the mill upwardly through each compartment, means for carryingoif the lighter particles of the material from the upper end of the chamber, and means for returning the heavier particles from the compartmentsy to the mill.

5. The combination with a pulverizing mill, of a chamber, nozzles communicating with the outlet of the mill and extending spirally upward into the chamber for conf- Veying the ground material from the mill to the interior of the chamber in a plurality of separate spiral streams, means for creating a current of air upwardly through said chamber and said streams' of material to carry offl the lighter particles, and permit the heavier particles to fall onto the bottom of the chamber, and pneumatic means for returning the heavier particles to the mill.

6. The combination with a pulverizing mill, of a chamber communicating with the outlet thereof and being circular in cross section, means for creating an up draft through said chamber, aA spirally extend ing nozzle rising from the bottom of the chamber and extending toward the side thereof and delivering substantially' at a tangent against the interior cylindrical wall of the chamber to deliver the material from the mill tangentially'against the circular wall and thus impart a whirling action to the issuing stream of material.

7. The combination with a pulverizing mill, of a separating chamber having a plurality of compartments in its lower end, each compartment having an inclined wall, nozzles projecting upwardly from the inclined walls into the chamber and communicating at their lower ends with the outlet of said mill to project ground material from the mill upwardly into the chamber, the coarse particles of the material being adapted to fall on said inclined walls, and return pipes leading from the lower ends of the walls to the mill kto return the j .coarse material thereto. f

8. The combination with a pulverizing mill, a separating chamber communicating therewith, av plurality of receivers. in the bottom vof said chamber adapted to receive the material from the mill, a plurality of nozzles extending spirally upward from the` receivers and terminating adjacent the inner Wall of the chamber and having their in the chamber.

9. The combination/with a pulverizing u 'mi1l, of a separating chamber having a plurality of compartments in the lower end thereof, each compartment having an inclined wall, nozzles extending through the inclined walls and communicatin at their lower ends with the outlet of sai mill and having their upper ends projecting spirally upward into the chamber above said inclined walls, means foil creating a suction upwardly through the chamber to feed the material from the mill and deliver it into the chamber in a plurality of separate spiral streams, and means at the lower ends of said'inclined walls to carry the coarser material dropping from the spiral streams back to the mill to be reground.

10. The combination with a pulverizing mill, of a chamber having 'a tapered chamber projecting upwardly into the chamber, nozzles communicating with the outlet of the mill and projecting spirally and upwardly from the sides of the said bottom into the chamber, means for feeding ground material from the mill upwardly through said nozzles into the chamber, the coarser material being adapted to fall back upon said tapered bottom, means for carrying olf the finer material from the chamber, and means fo-r'returning the coarser 'material from said bottomto the mill.

11. The combination with a pulverizing mill having an upwardly opening discharge throat, of a chamber connected to the throat,

Vthe free How of the material and the dropping of the heavy particles thereof on the inclined bottom, whereby the said particles atlberty to fallwinto the.bottom of thel chamber 20by` reason Aof this spreading out and dividing of the material. The disposition of the nozzles is such that the heavier particles cannot by gravity fall backwardly through the nozzles, but must drop oli-top of the receivers and be deflected by the oppositely inclined walls thereof into the bottoms of the various compartments. As the nozzles 22 are relatively small in diameter as compared with the cross sectional area of the-receivers and of the chamber 20, the material is given increased impetus or velocity in passing through the nozzles, so that the suction through the nozzles is comparatively great and \no chance is made possible of the blocking or clogging up of the nozzles.

Furthermore, the restricted areas of the nozzles effect the expulsion of the material therefrom with comparatively great force,

so that the material spreads outwardly froml the ends of the Inozzles and spreads into a relatively broad spiral stream. The induced current holds the finer particles in suspension and draws the same upwardly from the chamber 20, but allows the gradual fall of the heavier particles from the whirling, stream to thus effect the gradual and posi-v tive separation of the different grades of the material.

From the uptake chamber 20, the material is carried through the section 23 andfan 24.-, into the hopper 26. It is delivered in the hopper at one side thereof and substantially tangentially thereto, so that a whirling o'r spiral stream of air and material is produced. As the hopper 26 is relatively large, the force of the air suction or pressure is lost, and the material is permitted to drop into the bottom of the hopper, while the air is caused to pass upwardly through the relativelylarge end 28 of the return or pressure pipe 27. The air passes through the pipe 27, and through the branches 29 into the opposite sides of the casing 1 0, so as to return the' air substantially to the central portion of the rotary part of the mill, to thus take advantage of the suction created at the central portion of the mill, as the hammers 12 are revolved. Thisinward ow of air through the pipes 29 into the casing 10 creates a suction in the pipes 31, which communicate with the lower end of the chamber 20, so that the heavier particles of material which'fall into the bottom of the chamber and are deflected into the pipes 31, are positively drawn by the air 'current down into the inner ends or bottoms of the branches 29 and forced into the casing 10 of the mill, and into the path of the rotary hammers 12. It is thus observed that not` only is a thorough separation of the pulverized material effected, but also the material which has not been ground or pulverized to the desired state is positively returned to the mill to be recrushed, and the positive means of returning this material to be recrushed is also utilized in separating the particles.

It will thus be readily understood that a very eflicient, economical, and practical device is provided for separating Athe material and adjusting the device to produce a finished article of the desiredv fineness, and also that the material which is rejected by the 'separator is positively returned to the mill, without the provision of exterior or' secondary means. l

curved path and at the same time is drawn upwardly by the suction of the induced current, so that a whirling spiral action is imparted tothe material in the chamber 20. The chamber 20 may be provided with any number of pockets or compartments in the bottom, and any number of nozzles, which are sulicient to receive, and to eject the material and permit the choking of the device.

1t is, of course, understood that it is within the spirit of the invention to modify and change the above specifically set vforth structure, as far as is permissible within the scope of the following claims.

What is claimed is 1. The combination with a rotary pulverizing mill, provided at the top with an upwardly extending throat through which the material is delivered by 'centrifugal force,

of an uptake chamber Ihaving a. closed bottom, said bottom serving as a top for the throat, a nozzle communicating with they throat through the bottom and extending upwardly above the bottom to deli/ver the ground material tangentially within the chamber, means for drawing off the light particles of ground material from the top of the chamber, and means for returning the coarse particles of material from the bottom of the chamber to the mill.

2. The combination with a rotary pulverizing mill, of an uptake chamber having a closed bottom formed with a plurality of compartments, means for delivering the ground material fromthe mill against the underside of said bottom, a plurality of nozzles corresponding in number to the compartments and opening through said bottom and extending upwardly therefrom to deliver the ground material from beneath the bottom into the chamber over said compartments, means for drawing o the light particles of the ground material from the top of said chamber, and means for returning i the heavy particles from said compartments in the bottom of the chamber to the mill.

3. The combination with a pulverizing mill, of a separating chamber having a throat communicating with said mill and with an outlet pipe at its upper end, nozzles communicating with said throat and extending upwardly and circumferentially into said separating chamber,'means for creating a" upper end of the chamber, and means for returning the heavier particles from the compartmentsy to the mill.

5. The combination with a pulverizing mill, of a chamber, nozzles communicating with the outlet of the mill and extending spirally upward into thechamber for conveying the ground material from the mill to the interior of the chamber in a plurality of separate spiral streams, means for creating a current of air upwardly through said chamber and said streams of material to carry ofi' the lighter particles, and permit the heavier particles to fall onto the bottom of the chamber, and pneumatic means for returning the heavier particles to the mill.

6. The combination with a pulverizing mill, of a chamber communicating with the outlet thereof and being, circular in cross section, means for creating an up draft through said chamber, a' spirally extending nozzle rising from the bottom of the chamber and extending toward the side thereof and delivering substantially at a tangent against the interior cylindrical wall of the chamber to deliver the material from the mill tangentially against the circular wall and thus imparta whirling action to the issuing stream of material.

7. The combination with a pulverizing mill, of a separating chamber having a plurality of compartments. in its lower end, each compartment having an inclined wall, nozzles projecting upwardly from the inclined walls into the chamber and communicating at their lower ends with the outlet of said mill to project ground material from the mill upwardly into the chamber, the coarse particles of the material being adapted to fall on said inclined walls, and return pipes leading from the lower ends of the walls to the mill to return the I coarse material thereto. f

Y 8. The combination with a pulverizing mill, a separating chamber communicating therewith, av plurality of receivers. in the bottom of said chamber adapted to receive the material from the mill, a plurality of nozzles extending spirally upward from the receivers and terminating adjacent the inner wall of the chamber and having their outlets extending in one circular direction, and means for creating an up draft through the chamber to force Ythe material from the receivers through said' nozzles, whereby the material is adapted to issue in a plurality of circularly directed streams and break up into a relatively broad film within the chamber.

9. The combination/with a pulverizing 'A mill, of a separating chamber having a plurality of compartments in the lower end thereof, each compartment having an inclined wall, nozzles extending through the inclined walls and communicatin at their lower ends with the outlet of sai mill and having their upper ends projecting spirally 'upward into the chamber above said inclined walls, means foi creating a suction upwardly through the chamber tofeed the material from the mill and deliver it into the chamber in a plurality of separate spiral streams, and means at the lower ends of said inclined Ywalls to carry the coarser material dropping from the spiral streams back to the mill to be reground.

10. ,The combination with a` pulverizing mill, of a chamber having a tapered chamber projecting upwardly into the chamber, nozzles communicating with the outlet of the mill and projecting spirally and upwardlyfrom the sides of the said bottom into the chamber, means for feeding ground material from the mill upwardly through said nozzles into the chamber, the coarser material being adapted to fall back upon said' tapered bottom, means for carrying olf the finer material from the chamber, and means fo-rreturning the coarser ma terial from said bottomto the mill.

11. The combination with a pulverizing mill having an upwardly opening discharge throat, of a chamber connected to the throat, an inclined bottom in the chamber constituting a top for the throat, means for forcing the ground material upwardly through the throat against the top thereof, a nozzle extending upwardly from the top to carry off the material impinged thereagainst, said nozzle ext-ending spirally upward in the chamber and delivering the material tangentially against the side thereof and at a point above the upper end of the bottom to admit the free iow of the material and the drop- Y ping of the heavy particles thereof on the inclined bottom in the chamber atY the opofi the throat to check the upward flow ofthe material, a nozzle opening at one end through the' bottom to receive the "material therethrough, the nozzle opening at its opposite end above the inclined bottom and ad- )acent and at a tangent to the wall of the chamber whereby to deliver thematerial upwardly through the lchamber in a spiral stream, the heavy particles being adapted to drop on said inclined bottoml and movey downwardl thereover, and discharging means at t e lowerend of the bottom for, receiving the heavy particles and returning the same to the mill. f

13. The combination with a pulverizing mill having an upwardly opening throat, of a chamber at the upper end of the throat, `a bottom in the chamber comprising a plurality of inclined walls in the top of the throat, means for feeding material up through the throat from the mill and against said walls, nozzles leading ifrom the walls to receive the material thrown thereagainst, the nozzles extending spirally upward in the chamber and opening adjacent the wall thereof and above the upper ends of the inclined walls to deliver the material in Cyclonic fashion into the chamber the heavier particles being adapted to fall on the bottom and move downwardly over the inclined walls, and discharge pipes opening at the lower ends of the Walls to receive the heavier particles and return the same to the mill. e

14. The combination with a pulverizin mill having an upwardly opening throat, o a chamber at the upper end of the throat, a bottom in the cham extending inverted- V-shaped --walls presenting oppositely inclined sides at their. upper faces and presenting converging lower sides at the top of the throat, meansv for feeding the ground material u wardly through the v throat against said'V-s aped walls, a nozzle carried at one sideof each V- shaped wall and extending' laterally 'and-upwardly at er comprising .radially substantially right angles thereto for the re- -ception of the material impinged againstl the lower faces of the walls, said nozzles exsal tending upwardly and outwardly to a point above the upper edges of the walls'and adjacent the inner wall of thechamber to deliver the material at substantially a tangent l against the inner wall of the chamber andabove the bottom whereby the material may freely issue from the nozzles and the heavier particles may fall upon the bottom and v Vshaped walls thereof, and discharge pipes -move .downwardly in oppositedirections i s "er the inclined faces of the inverted V- opening at the lower ends of said walls to receive the downwardly moving materialand leading to the inlet of said mill toreturn the heavier particles thereto.

mill having an upwardly opening discharge throat, of a chamber connected to the throat,

the throat, means for feeding ground material upwardly through the throat and '15 i l15. The combinationwith a pulverizing.

an inclined wall between the chamber and v L against said inclined wall,.a nozzle opening through'the wall and extending into 'the chamber above the wall to receive the material impinged against the wall and deliver the .same into the chamber, the heavier particles. dropping on said inclined wallx and falling downwardly thereover, and return-f p from the bottom of the wall to the inlet o said mill and adapted to ing means leadin receive thefalling same tothe millto ereground.

16. A dust separator comprising aA casing' having discharge means for the tailings 1ocated at the lower end thereof, an outlet for the fines leading from the upperportion articles and returnthe thereof, an inlet conduit for the dust-laden air leading into the lower portion of said casing, elbow` pipes arranged on the 'upper end of said in et conduit within the casing,

said elbow pipes having their free end portions curved and terminating above the discharge `means for the tailings andinclined y upwardly and laterally whereby ,the talin are first thrown upwardly and tangential y' against the vertical walls of the-casing. .In testimony that'l claim the foregoing as my own, I have hereto affixed my .signature inthepresence of two witnesses.

EDWARD' J. s'rncina; witnesses: .Y A:- E. V

.Gnomz-naw. GnHoUT 

